This invention relates generally to electrical machines and more particularly, to methods and apparatus for assembling electrical machines.
Generally, a wind turbine generator includes a turbine that has a rotor that includes a rotatable hub assembly having multiple blades. The blades transform wind energy into a mechanical rotational torque that drives one or more generators via the rotor. The generators are generally, but not always, rotationally coupled to the rotor through a gearbox. The gearbox steps up the inherently low rotational speed of the rotor for the generator to efficiently convert the rotational mechanical energy to electrical energy, which is fed into a utility grid via at least one electrical connection. Gearless direct drive wind turbine generators also exist. The rotor, generator, gearbox and other components are typically mounted within a housing, or nacelle, that is positioned on top of a base that may be a truss or tubular tower.
Some wind turbine generator configurations include doubly fed induction generators (DFIGs). Such configurations may also include power converters that are used to convert a frequency of generated electric power to a frequency substantially similar to a utility grid frequency. Moreover, such converters, in conjunction with the DFIG, also transmit electric power between the utility grid and the generator as well as transmit generator excitation power to a wound generator rotor from one of the connections to the electric utility grid connection. Alternatively, some wind turbine generator configurations include, but are not limited to, alternative types of induction generators, permanent magnet (PM) synchronous generators and electrically-excited synchronous generators and switched reluctance generators. These alternative configurations may also include power converters that are used to convert the frequencies as described above and transmit electrical power between the utility grid and the generator. These wind turbine generator configurations rely upon accurate generator rotor position/speed indications to facilitate generator control.
Many known wind turbine generators use rotor position encoders and/or transducers to measure rotor position/speed. However, such encoder and transducer configurations include additional hardware such as shaft couplings, interface electronics and connecting cabling between them. Moreover, such configurations may also include mechanical mounting hardware such as mounting flanges, adaptor plates, and fasteners. In some wind turbine generator configurations, remote positioning of wind turbine generator control systems may facilitate cabling lengths in excess of 91 meters (m) (300 feet (ft)). Some wind turbine generators require parallel redundant systems which increase capital costs. Moreover, such redundancy increases operational and maintenance costs. Furthermore, excluding use of such redundant systems decreases operational reliability.